That a control plane is separated from a forwarding plane is a basic feature of an SDN (Software-Defined Networking)/OpenFlow. A routing policy is formulated for the control plane based on a network-wide view, and a data packet is processed on the forwarding plane according to a received routing policy. To establish a TCP connection between an OFS (OpenFlow switch) and an OFC (OpenFlow controller) is a basic premise on which an OpenFlow network can work normally.
Currently, an out-of-band connection mode is generally used between the OFS and the OFC. FIG. 1 is a networking diagram of an existing out-of-band connection mode. The control plane and the forwarding plane include two different physical networks each. The control plane includes switches Switch, OFS1, OFS2, OFS3, OFS4, OFS5, and OFS6, and a controller OF_Controller, and a data plane (this means a forwarding plane) includes switches OFS1, OFS2, OFS3, OFS4, OFS5, and OFS6.
In a network shown in FIG. 1, the Switch first connects to the control plane based on protocols such as LLDP and STP in a working mode of a traditional switch, that is, the Switch implements forwarding of various OpenFlow control messages by using a MAC table generated by protocols such as STP, where the control messages refer to various messages such as a Controller-to-Switch message, an Asynchronous message, and a Symmetric message that are defined in the OpenFlow specification. After the Switch is connected to the control plane, the OFC may deliver an initial flow entry to the OFS. After receiving the flow entry, the OFS adds the flow entry to a corresponding flow table, so that a data packet can be processed according to the flow table.
A main disadvantage of this solution is that two independent physical networks and two network management systems (one is used to manage a network on the control plane, and the other is used to manage a flow switching network on the forwarding plane) need to be maintained, and costs are relatively high.